Transcript RADIATION PROTECTION IN DIAGNOSTIC RADIOLOGY

IAEA Training Material on Radiation Protection in Diagnostic and Interventional Radiology
RADIATION PROTECTION IN
DIAGNOSTIC AND
INTERVENTIONAL RADIOLOGY
Part 15.6: Optimization of protection in
radiography
Practical exercise
IAEA
International Atomic Energy Agency
Overview
• Subject matter: quality control of
general radiography system
• Step by step procedure to be followed
to implement the considered QC test
• Beam collimation and Bucky tray
alignment
• Interpretation of results
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IAEA Training Material on Radiation Protection in Diagnostic and Interventional Radiology
Part 15.6: Optimization of protection in
radiography
Beam collimation and Bucky tray alignment
IAEA
International Atomic Energy Agency
What Minimum Equipment is Needed?
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6 coins
24 X 30 cm cassette
Film
Ruler
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Light Field/X-Ray Field Alignment
• Method:
• place loaded cassette on table at 100 cm focus•
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film distance (FFD)
collimate to ~ 20 x 20 cm field
place metal markers (e.g., coins) at each field
edge plus one at anode end, and one at top of
field
make an exposure of ~5 mAs at 70 kVp
develop the film
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Light Field/X-Ray Field Alignment
Anode marker
Orientation marker
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Coins
Light field
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Alternative Method
• Place two coins at each edge - touching at the light
field edge
• Make a slightly lower exposure, then open the light
beam to include both coins, and take another
exposure, about half the mAs of the first
• This makes the coins visible even if the x-ray field
is significantly mis-aligned
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Alternative Method Light Field Set for Second Exposure
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Light Field/X-Ray Field Alignment
Analysis :
• assure that you can see each coin
• measure the distance between the coin and the
x-ray beam edge
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Light Field/X-Ray Field Alignment
Alignment error
Coin
shadows
X-ray Field
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Exposed Film - Alternative Method
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Acceptance limits
• Light and x-ray field alignment should be within
2% of the source-to-image (cassette) distance.
• Ideally, the alignment should be within 1%.
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Where to Get More Information
Quality Control in Diagnostic Imaging, Gray JE,
Winkler NT, Stears J, Frank ED. Available at no
cost. http://www.diquad.com/QC%20Book.html
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